The invention relates to an electronic semiconductor device having a thermal spreader.
As is known, containers for devices which have to dissipate a certain quantity of heat have a thermal spreader element. The thermal spreader may be formed by a metal region fixed to a ceramic base then fixed to the device or by a portion of the lead frame.
For a thermal spreader using a ceramic base, two fixing operations are required: a first operation to bond the metal region to the ceramic base and a second operation to attach the device to the metal region; consequently the fixing costs are considerable. Furthermore, this solution involves considerable space: indeed, to ensure that the device and the metal region overlap under all conditions and to prevent undesirable short-circuits even in presence of possible misalignments, the metal region has a larger area than the device; furthermore, the electrical connection wires which connect suitable conductive areas formed on the ceramic base to the contact pads of the device need to be formed at a certain distance from the metal region. Overall, therefore, the area required on the ceramic base for fixing and connecting the device is considerably larger than the area of the device. This solution further requires the manufacture of long connection wires, which is undesirable.
Forming the thermal spreader directly on the lead frame has the following disadvantages: the chip/base assembly has two interfaces; a first interface is present between the chip and the lead frame and a second interface is present between the lead frame and the ceramic base. The connection between the chip and the printed circuit requires two wires in series and thus has greater resistance.
According to the invention, there are provided an electronic device and a relative manufacturing process.
In a preferred embodiment of the invention, the electronic device is formed as one of a plurality of electronic devices formed on a wafer. Prior to cutting the wafer into dice, an integral thermal spreader of metal is galvanically grown on a lower surface of the wafer, and a covering structure, which comprises a passivation region and a protective region of opaque polyimide is formed on an upper surface of the wafer. The protective region and the passivation region are opened above the contact pads for the passage of leads.